Timed execGit commands lead their own POSIX process group, so nothing
reached a probe still running when the app quit: the 5 s timer died with
the process and the group was left orphaned under PID 1 (#125243's
"survives restart"). execGit now tracks timed children, and will-quit
kills each tree (group SIGKILL on POSIX, taskkill /T /F on Windows).
On Windows a root that already exited has no tree left for taskkill /T to
walk and its pid may be reused, so the timeout path skips taskkill there.
The error/close handlers no longer repeat finish()'s clearTimeout.
Quit-time cleanup was first proposed in #125861.
Co-authored-by: chelsealong <chelsealong@126.com>
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